1. Technical Field
The present disclosure relates to an image capturing apparatus having camera shake correction function.
2. Related Art
As a camera shake correction device for an image capturing apparatus such as a digital still camera, a device is known which has an image stabilizing lens movably arranged on a plane orthogonal to an optical axis of a optical system and drives the image stabilizing lens with an actuator in a direction to cancel a vibration when the vibration is applied to the camera (the optical system) to correct the camera shake. Such a camera shake correction device detects the vibration applied to the camera with an angular velocity sensor, integrates a shake signal output from the angular velocity sensor to calculate displacement of the image stabilizing lens for correcting the camera shake, and drives the image stabilizing lens with an actuator such as a voice coil motor or a stepping motor.
Usually, a frequency of the camera shake caused by human hands holding the camera mainly contains frequency components of around 1 Hz, and it has the frequency bandwidth of 0.1 hertz to tens of hertz. Thus the frequency of the camera shake also contains quite low frequency components as well. Therefore, the angular velocity sensor is required to have a sensitivity high enough to detect such a low frequency but increasing the sensitivity causes the angular velocity sensor to be too sensitive to disturbance. That is, a digital still camera has a problem in that, due to disturbance such as impact, the angular velocity sensor makes false detection of a vibration other than the camera shake.
For example, a single lens camera has impact made by a focal-plane shutter running. The angular velocity sensor is likely to make false detection when such impact is applied to the camera. Since a correcting unit for correcting camera shake operates according to the output from the angular velocity sensor, the false detection by the sensor may lead to a wrong correction by the correcting unit, degrading a captured subject image. In view of the above, some methods for preventing image degradation led by false detection due to shutter-induced impact have been proposed.
For example, JP 4-158342 A discloses techniques for increasing time constant of a high frequency cutoff filter provided in signal processing of the signal from the angular velocity sensor to reduce false detection due to the shutter impact, and for decreasing a gain set in a gain controller to suppress movements of the camera shake correction lens.
The technique for increasing the time constant of the high frequency cutoff filter causes phase lag in the above described camera shake correction band, delaying operation of the camera shake correction lens with respect to the actual camera shake, and therefore, sufficient camera shake correction effect cannot be obtained.
The technique for decreasing the gain set in the gain controller reduces movement of the camera shake correction lens due to the shutter-induced impact, but also reduces the correction amount, of the real camera shake, which lowers the camera shake correction effect.
An object of the present disclosure is to provide a camera shake correction technique capable of reducing the false detection caused by high-frequency vibration such as shutter-induced impact in detecting camera shake, and an image capturing apparatus having the technique.